1. Field of the Invention
The present invention relates to a tape adhering method for adhering a tape, for example, a dicing tape onto a back surface of a wafer. The present invention also relates to a tape adhering device of executing this tape adhering method.
2. Description of the Related Art
In the field of manufacturing semiconductors, there is a tendency for large-sized wafers to be used year after year. Further, in order to enhance the packing density, the wafer thickness is reduced, and in order to reduce the wafer thickness, the back surface of a semiconductor wafer is ground. At the time of back-grinding, in order to protect a semiconductor element formed on a front surface of the wafer, a surface protection film is adhered to the front surface of the wafer.
When back-grinding is conducted on the wafer, the wafer is greatly reduced in thickness. Therefore, a dicing tape is adhered to the back surface of the wafer so that the wafer can be integrated with a mount frame into one body. When the wafer is integrated with the mount frame, the wafer can be easily handled in the next step.
Japanese Unexamined Patent Publication No. 2006-044152 discloses a adhering device in which a tape is drawn out onto a mount frame and a wafer so as to adhere the tape. The tape drawn out from a tape roller is guided by a guide member and adhered to a neighborhood of an edge portion of the mount frame at first by an adhering roller.
FIG. 6 is a top face view of a wafer in the case where adhering operation of a tape onto a mount frame is started in the prior art, such as disclosed in Japanese Unexamined Patent Publication No. 2006-044152. At the time of adhering as shown in FIG. 6, the tape 3 is adhered only to an adhering portion 3a located in the neighborhood of an edge portion of the mount frame 36.
Next, a table (not shown) for supporting the mount frame 36 and the wafer 20 is moved in the horizontal direction. Due to the foregoing, the tape 3 is adhered to the entire mount frame 36 and wafer 20.
However, at the beginning of adhering the tape 3 to the mount frame 36, the area of the adhering portion 3a is relatively small. Therefore, this is a case in which the tension of the tape 3 given by the tape roller exceeds the adhesive force at the adhering portion 3a. In this case, when the tension given to the tape 3 exceeds the elastic limit of the tape 3, wrinkles 99 extending in the longitudinal direction are formed on the tape outside both end portions 3b, 3c of the adhering portion 3a as shown in FIG. 6. Since these wrinkles 99 are formed on the tape 3 as a result of the tension that has exceeded the elastic limit of the tape 3, when the wrinkles 99 are formed, it is impossible to remove the wrinkles even after the tension given by the tape roller has been released.
In this connection, FIG. 7 is a view showing a state of a common tape roller. A draw-out position of the dicing tape 3, which is drawn out right after the tape roller 142 has been loaded into an adhering device, is located relatively outside in the radial direction. When the adhering operation of the dicing tape 3 progresses and the amount of the dicing tape 3 remaining on the tape roller 142 is reduced, the draw-out position of the dicing tape 3 is gradually moved inside in the radial direction. Concerning this matter, refer to the imaginary line 3′ in FIG. 7. In the case where the draw-out position of the dicing tape 3 is located relatively outside, in order to prevent the tape roller 142 from over-running, it is necessary to arrange a braking mechanism (not shown) adjacent to the tape roller 142.
Due to the foregoing, right after the tape roller 142 has been loaded and right before the tape roller 142 is replaced, the intensity of the drive torque needed for rotating the tape roller 142 is different. The intensity of the drive torque right after the tape roller 142 has been loaded is considerably higher than the intensity of the drive torque right before the tape roller 142 is replaced. Therefore, the intensity of the tension given to the tape by the tape roller right after the tape roller 142 has been loaded is considerably high. As a result, right after the tape roller 142 has been loaded, wrinkles 99 described previously tend to form on the tape 3. Further, when the tension greatly exceeds the adhesive force at the adhering portion 3a, the tape 3, which has been adhered to the adhering portion 3a, may be detached from the mount frame 36.
The present invention has been accomplished in view of the above circumstances. It is an object of the present invention to provide a tape adhering method capable of preventing the formation of wrinkles. It is another object of the present invention to provide a tape adhering device in which this tape adhering method is executed.